Calender rolls



June 29, 1965 H. E. KUEHN 3,191,263

u GALENDER ROLLS Filedoct. 2s, 1962 v 2 sheets-sheet 1 91j/ IG Howard E.. Huehn ATTORNEYS H. E. KUEHN CALENDER ROLLS June 29, 1965 Filed Oct. 23, 1962 INVENTOR Howard E. Huehn BY g MW WM# ATTORNEYS United States Patent O 3,191,263 QALENDER ROLLS Howard E. Knehn, Grange, Conn., assigner to Farrel- Birmingharn Company, Incorporated, Artsonia, Conn. Filed st. 23, w62, Ser. No. 232,547 1f) Ciairns. (ill. 29-l21) This invent-ion relates to calenders and like devices and more particularly relates to compensation of calender -rolls to control the effective crown thereon.

In machines such as calenders designed for rolling relatively ythin sheet material, one or more rolls of the calender may be designed with a crown thereon in order to compensate for the bending and deflection of the rolls Iintermediate their ends due to the considerable pressure exerted upon these rolls during operation. The degree of crown given to the rolls is selected to be that which will bring about a substantially parallel arrangement of the cooperating roll surfaces during operation thereof. rIhe degree of crown with which the rolls will be provided depends upon the pressure under which they operate plus other operating conditions which may include the type of material being rolled as well as the characteristics and dimensions of the rolls. Therefore, for optimum results it may be necessary to provide rolls with different crowns for different operating conditions.

Where calendering machines are required to roll different types of sheet material the crown provided on the rolls may be the optimum crown for one of the materials While lthe same crown would not be the optimum for other materials.

To provide various crowns on calender rolls for various operating conditions of the calender the effective crown of the rolls may be varied by crossing the axes of cooperating rolls so that the axes of the crossed rolls form equal acute angles and the rolls are wider spaced at their ends than at their center. To accomplish roll axis crossing, at least one of two cooperating rolls is moved about a point intermediate the roll ends so as to bring about a nonparallel relation of the roll axes to effect what is commonly termed, a cross-axis relationship. A calender having facility for crossing the axes of cooperating rolls is disclosed and claimed in United States Patent 2,965,920 of Warren C. Whittum, assigned to the same assignee as the present application.

Another technique of providing crown compensation of calender rolls is to bend the rolls so as to provide an effective crown thereon. Roll bending may be accomplished by exerting forces on the roll necks outboard of their point of support in the calender frame. The forces exerted on the roll necks act in the same direction to produce a bending moment of the roll about its points of support and may be in such a direction as to either provide a convex working surface on the roll or a concave one. A calender having facility for roll bending is disclosed in U.S. Patent 2,611,150.

Both of aforementioned techniques of crown control, axis crossing and roll bending, provide an effective crown on a roll which in many applications is satisfactory, however, neither of these techniques of crown compensation give an effective crown contour equal to the optimum crown contour that would be utilized if an optimum crown contour could be selected for each operating condition of the calender. An optimum crown contour, as hereinafter pointed out, has been well established by theoretical and empirical techniques and is quite well known to those skilled in the art of calendering operations. If the crown contour or the effective crown contour is not within a given tolerance which may be very small, then a substantially uniform nip pressure across the faces of the cooperating calender rolls is not ob- 3,f9l,263 Patented .lune 29, 1965 tained and varying degrees of unsatisfactory operation may occur dependent upon the tolerances allowed in the thickness of the sheet material rolled by the calender. For example, if a calender is rolling a very thin sheet of material, a deviation in the thickness of the material of several ten-thousandths of an inch can be very critical, whereas in rolling a thick sheet or board such deviation would be insignificant.

Many times, in practice, the most critical material to be rolled on a calender needing the most accurate total crown, is not rolled at the particular crown on the roll as ground, i.e., the original crown. Therefore, the original crown requires modification which may be provided by roll axis crossing or roll bending. Such modification, however, provides an effective crown contour which departs from the desired crown contour.

By practice of the present invention, a calender roll arranged for cross-axis or roll-bending crown control may be properly compensated to provide an effective crown corresponding to a desired crown contour. The present invention provides calender rolls having a crown contour which compensates for deviations in an effective crown obtained by crossing the axes of cooperating rolls or roll bending.

Accordingly, it is a primary object of this invention to provide rolls for a calendering machine which may havel an effective crown established therebetween which coincides very precisely with a desired crown contour necessary to maintain a uniform pressure on material being rolled across the width thereof.

In accordance with this invention, calender rolls are so contoured that if it should be desired to vary lthe effective crown thereon as for example, by roll-axis crossing or roll bending, the effective crown provided thereby on cooperating rolls will very accurately coincide with an optimum crown contour selected in accordance with the deflection curve of a loaded beam.

The novel features of the invention are pointed out with particularly in the claims appended to and forming part of this specification. However, the invention, as to its organization, together with further objects and advantages thereof, may best be appreciated by reference to the following description taken in conjunction with the drawings wherein:

FIG. 1 illustrates, in front elevation, the rolls of a calendar.

FIG. 2 is a view seen along line 2 2 of FIG. l with the axis of the bottom roll crossed with respect to the roll immediately above.

FIG. 3 is an end View of the calender rolls of FIG. 2.

FIG. 4 illustrates the effective crown obtained on a calender roll by roll axis crossing.

FIG. 5 illustrates crown contours obtained by roll axis crossing and an optimum crown contour originally ground on a calender roll in accordance with a calculated deflection curve.

FIGS. 6 and 7 illustrate calender rolls provided with crowns in accordance with the invention.

FIG. 8 illustrates, in front elevation, the rolls of a calender wherein the lower roll is adapted to have an effective crown provided thereon by roll bending.

FIGS. 9 and l0 illustrate lower calender rolls having effective crown provided thereon by roll bending.

FIG. 11 illustrates the effective crown provided on a roll by roll bending.

FIG. l2 illustrates a calender roll adapted for roll bending and having a compensated crown contour in accordance with the invention.

FIG. 13 is a graphic illustration of a crown contour obtained through roll bending.

The primary objective in crowning rolls is to compensate for bending l,of the rolls intermediate their ends under the considerable pressure exerted on these rolls during operationof the rolls and thus obtain a uniform dis-r i tribution of pressure at the roll nip. The crown shape recommended andused as an optimum or target curve forv a calender roll isillustrated by curve C, FIG.!5, and the degree of crown at points along its length are expressed Y in termsof the maximum crown as hereinafter exemplified. This optimum or targetcurve is determined from the' gener-al equation for the defiection of a symmetrical beam ontwo supports with a 'distributed load evenly spaced therebetween which may be found in Machinerys Handbook, 16th Edition, page 398, and hereinafter will be referred to as a deflection-curve crown.k ,In the exam ple given below in Table I', thel deflection-curve crown illustrated is for a roll having an A /L rat-io, asV illustrated in FIG. 1, of '.12, where L is-thev length of the roll face and A is the distance from zthe ends of the rollface to the center lnesofv support ofthe roll journals.

L=Length of roll x=an arbitary distance from end of roll C=horizontal distance between crossed axis 22 `and 23 at distance x The effective crownl contourwhich may be determined from Equation 4' is shownin Table II below.

The crown curve for a calender roll having an A/L value of .12 was selected for illustration inasmuch as this value is the one most commonly used in industry. For further examplefthe percent of total crown of a deectio'n-curveV 4crown Yat the point midway` between `the end Tof a roll and the center line thereof will vary between .7209 and '.7309 of the maximum crown for A/L values between .06 and .20. A general discussion on roll crowning may be found in Paper Trade Journal,,July 18, 1960, pagesl application of crowns to rolls often becomes a compro- V mise dictated bythe range of materials to be rolled. is, of course, much better to base a compromise on exact knowledge of what thel'cor'rect conditions shouldv be, because conditions can then be altered with greater certainty of obtaining the best results. V The effective crown curve, of aroll Amay be varied by crossing the axis of one roll with respect to another' as explained in U.S. Patent 2,965,920, assigned'tovthe' same assignee as the ,present invention, however, the' effective crown obtainedby rollaxis crossing varies from the deection-crown curve withresulting nonuniformity yin nip pressure between the rolls. f Y

To illustrate the'v deviation between an'e'ffective crown obtained by roll a'xisvcrossing and the crown correspondfing to the deflection curve, consider the calender 14' of Withreference to FIG. 2 Aand FIG. 3f, whichjis Va dia- 'gramatic end view of therolls of FIG.2, let y. y=distance orgap between surfaces `ofcr'ossed axis rolls 1D=distance between axis of rolls:in uncrossed condition CT=horizontal distance between vcrossed'axes atend of rolls l f Y i Table Il Fraction of'distancealong Fraction of Deflection roll from end to center is- Gap y,'in. total ecccurve crown tiveerown fronr'lablc I e. 0249 0 0 Y. 0203 1 170 0159 961r 331 0122' 510 478 .0089 .642 .611 .0062 751 726 0040iv 8394 823 0022 912 .,899 0010 960 955 ,-0002 992r 989 0 1.0 1.0

It will'be notedy that the effective crown curve obtained from rollf.axis crossing as exemplified by `curve B, FIG. 5, varies apprcciably from the v'optimum or deflection curve crown Aas exemplied by curve C, FIG. 5, particularly, intermediate the center and endA of the roll as is further evidenced by comparison of the crown contours of Tables I and II. In FIG. 5, ythe point one half fof the distance from the end of the rol'l'totheY center has been selected to numericallyA indicate the deviation of an effectiver crown contour from Vdeflection=curve crown contour. y y

Therefore, in accordance with lthe invention where a calender is kprovided havingfacility for cross-axis crown control, it will be modified by the difference in the target or defiectionr curve andthe effective crownl contouras exemplified by the difference in crown curves C and B, PIG. A5. v

FIG. lvillustratesa pair ofcooperatnig rolls 24v and 25 wherein the bottom roll 25 is ,arrangedI to have its axis crossed with respect to the axis of ,rollj241 In FIG. 4, roll 25` which originally'was ground with a deflectioncurve crown and, when utilized with its axis crossed with vrespect' `to roll 24, produces an undesired effective crown l215., as illustratedandvuniforrn nipfpressure will not be achieved' across the vface of the rolls 24v and 25 and the materiall Mvbeing rolled will not attainla uniform thickness( It may be noted that therewill-be high Aareas 27 and 28 in the effective' crown .296, intermediate V4the ends andthe center of the rolls. v

FIG. -6`illustratesl acalender .roll -29 having a crown ground'thereon, inaccordance-with the deflection curve, as exemplified by broken line 30,5 modified by the differ- '.ence in the deflection-curve crown andthe effective crown obtained byl roll axis Vcrossing,as lexemplified by theA full Vline crown. The 4deflection-curve.crown is indicated by the referencenumeral 30', `andl the final rmodified crown curve is indicated by the reference numeral 31. It will be noted that the roll 29 of FIG. 6, in accordance with the invention has some of the deflection-curve crown removed in the areas corresponding to the difference between crown curves C and B, FIG. 5.

FIG. 7 illustrates the manner in which a normally cylindrical roll 32 adapted for cross axis operation will have its crown contour 33 modified from a cylindrical shape 34 in acordance with the invention so that when it is operated with its axis crossed, an effective crown equivalent to the deflection-curve crown will be obtained.

It is to be understood that throughout the drawings, for clarity of illustration, the crown contours are exaggerated.

It may also be shown that the effective crown obtained by roll bending, as exemplified in FIGS. 8 and 9, deviates from the deflection-curve crown contour as determined by the beam deflection method, and the invention also contemplates compensation for such deviation. A calendar having facility for roll bending or unbending to vary the effective crown of' a roll is disclosed in U.S. Patent 2,611,150.

FIG. 8 illustrates a calender 35 comprising a bottom roll 36 having journals 37a and 37b which support roll 36 at points equidistant from each end of the face thereof on bearings 38 and 39. Pressure rollers t0-45 are mounted vertically above roll 36. Roll 36 is arranged to be bent by forces applied to the extending ends of its journals equidistant from the center of support of journals 37a and 37b, as represented by the downwardly directed vectors 46 of equal magnitude and the upwardly directed vectors 47 of equal magnitude. FIG. 9 illustrates bending of roll 36 by application of downwardly directed forces on the extending ends of its journals to provide an effective crown curve 48 thereon. It will be noted that the applied forces 46, together with the reaction exerted on the journals by bearings 38 and 39 produce oppositely directed force couples at either end of the roll.

The face of roll 36 when roll 36 is bent, as illustrated in FIG. 9, is shown in FIG. 13 set on a coordinate x-y axis. The contour of the crown on the roll 36 resulting from roll bending will be a true arc of a circle of radius R where R=EI (n It may be shown that where E=modulus of elasticity of the roll I :moment of inertia M :bending moment See Mechanics of Material, Lawson and Cox, 2nd edition, 1950, Wiley and Sons, pp. 155-158.

Table III Fraction o distance from Fraction of Crown curve due end of roll to center total crown to axes crossing (from Table Il) It will be noted that the effective crown contour obtained by roll bending is almost identical to the effective crown contour obtained by crossing roll axes as pointed out in Table II. Therefore, for purpose of discussion, curve B of FIG. 5 may be considered to also represent an effective crown due to roll bending.

In some instances the crown on a roll may be decreased by roll unbending as illustrated in FIG. 10 to obtain a net crown 49 of less magnitude than initially applied to the roll 36. The purpose of unbending the roll is to reduce the magnitude of the original crown on the roll Iby an amount required to obtain a smaller magnitude crown for rolling a material requiring less nip pressure. However, unless the roll 36 has a crown contour properly compensated for roll bending, the resulting crown 5t) would appear as shown in FIG. 11 and the nip pressure between the faces of rolls 36 and 40 will not be uniform across the faces thereof and the material M being rolled will not have a uniform thickness.

FIG. 12 illustrates a roll S1., contoured in accordance with the invention, arranged for roll unbending or decrowning crown compensation as exemplified in FIG. 10. The contour or outline of roll 51 is a composite `of a deflection-curve crown in accordance with the 4defiection curve, as exemplified by the broken line S2, with additional crown 53, S4 superimposed thereon to provide an effective crown on roll 51, which in roll unbending operation would achieve the contour of the desired deflection-curve crown. In FIG. 12, the additional crown 53, 54 added to deflection curve crown 52 is the difference in the crown contours of Tables I and III.

If a calender roll having the normal deflection-curve crown contour were to be used for roll bending crown control as exemplified by FIG. 9, it would, in accordance with the invention, have a crown provided thereon derived from subtracting the difference of the crown contours of Tables I and III from the deflection-curve-contour of Table I which would produce a crown contour as exemplified in full line in FIG. v6.

In the crown contours discussed, the total magnitude of a given crown on a calender roll has not been specifically discussed and it will be lapparent that the absolute magnitude of a given crown will depend on such parameters as the dimensions of the roll, the pressure exerted thereon, etc. For purposes of illustration only, Where a roll has an effective crown change asV a result of .roll axis crossing -or roll bending which amounts to .020 at a distance midway between the center and end of the roll face, the

difference -between curves 30 and 31 (FIG. 6) wouldv be The same v `:glances in crown of .0004" initially appears to be a relatively small one, it may be very significant in rolling a very sheet of material to a uniform thickness.

In any of the cases discussed, roll axis crossing, roll bending 4or roll punbending, the reason for such provision of an effective roll crown is to obtain :a series of crowns to suit a range of `different materials to be processed on a given calender. Dilferent materials to be processed require different pressures, less cr-own being `required for materials requiring lesser pressure and vice versa. It will be understood that the entirek difference between the crown contours, as exemplified by curves C. and B, may

thin

, not be added `to or subtracted Vfrom a roll,.but,someV predetermined percentage of thi-s differencemaybe added to or lsubtractedv from a r-oll in Iaccordance with design considerations `of the roll and the types o f materials to be processed. While the invention has beendisclosed as applied to the bottom r-oll of a calender, it-isjto be understood that it is equally applicable whererolls other than the bottom rolls .are to be bentror operatedwith crossed axes to provide an eifective crown.

While the invention has been disclosed invar-ious embodiments thereof, it will be apparent that the invention may be practiced with various apparatus rdesigned to effect roll cross axis and roll bending crownv compensati-on, and it is intended to cover in the appended claims all embodiments of the invention andv modifications of the disclosed invention which do not `depart from the spirit Iand scope of the invention.

What is claimed is:

1. For use in a calender or like device having :a plurality of cooperating rolls vand having at least one yroll adapted to have its axis crossed with respect tothe axis of a cooperating roll to provide an effective crown on Said one roll; a calender roll having a contour along its face predetermined by the difference between a crown contour based upon the shape `lof a uniformly loaded beam between two points of support, and :an effective crown defined by the distance between adjacent surfaces of a pair of cooperating uniform diameter rolls arranged for cross axes operation. y

`2. The calender roll of claim l1 wherein said calender roll has a crown contour along the face thereof predetermined in accordance with .the shape of `a uniformly loaded beam for a given A/VL value of said roll, said crown Vcontour being reduced proportional to the difference between said loaded beam `crown contour and an effective crown deiined by the distance between adjacent:

roll has a cylindrical contour reduced proportional to length' of the faceiof the roll and A is the distance from face to the center A/L value Vof said roll and an effective crown dened by the distance between adjacent surfaces Iof a pair of V-cooperating. uniform'diarneter rolls arranged for cross 4axes operation, where L is the length of the face of the roll and A is the distance fromthe one end of the roll of support of the roll journal at that end.

4. For use in a calender or like device having aplurality of cooperating rolls Vand having at least :one roll :adapted -to be bent by applying oppositelydirected'force couples at opposite' ends thereof to delinelan effective crown thereon having fa shape whichis substantially an l arc of a circle; a calender roll having a crown contour along its face predetermined bythe difference between a crown contour which Yis substantially an arc of .a circle n and acrown .contour based upon the shape of a beam n which/is uniformly' loaded between two pointsof support.

5.V The calender roll of claim i4 vwherein said predetermined diference in contour isaddefd to` the contour of said `calender roll.

6. The calender roll o'f claim 4 wherein said predeterminedV difference in contour -is-subtracted from' the contour of said calender roll."

7. The calender roll' of claim 4 'wherein' said calender r'oll has :a crown contour thereon 'based uponI the shape of a beam which is uniformly loaded betweenvtwo points or support for a given A/L value o'f said roll, ysaid fc'rownl 'contour' being yreduced,proportional to rvthe" difference between said crown contour and a crownfcontour which is substantially an :arc of a circle',.whe're L is'the the' one .end oftheI vroll face'to vthe center of supportof 8. The` calender roll -oficlairn 4 wherein said calender 'r-oll has fa crown conteur thereonv based on the'shap'e of a' beam which is uniformly loaded between two-,points y 'of' support for :a given A/L value ofsaid rollgsaid load- `ed beam crown contour beingincreased"proportional to the Vdifference `between said loaded `beam crown 'contour vand. a crown contour which -is Substantially an 'arc of a circle, whereLi-s the length ofthewface of the rolland is the ,distancefromthe one Yend ofthe roll lface to Vthe vcenter of support of the` rfoll' journalat that end.'

Y shape of a beam which is'uiformly loaded between two points `of support and a crown contour which is substantially an arc of a circle, where 'L is the length of the -face of the roll and A is the distance from the one end of the roll face to the center'of support of 4the roll journal at that end.

7o 3. The calender roll vof claim 1 wherein said 'calender the difference between said loaded beam shape for a given 10. The calender roll of claim 4 wherein lsaid roll has a cylindrical contourwhich is increasedl proportionalto the diierence between a crown contour based .upon the shape of :abeam which is uniformly. loaded between two points of support and acrowncontour which issubstantially an arc of a circle fora given A/L value of saidroll, where L is the length of the face of the roll and A is the distance from the one end of the roll face to the center -of support of the. roll journal at that end.

VReferences Cited by the Examiner UNITED STATES PATENTS WALTER A. SCHEEL, Primary Examiner. 

1. FOR USE IN A CALENDER OR LIKE DEVICE HAVING A PLURALITY OF COOPERATING ROLLS AND HAVING AT LEAST ONE ROLL ADAPTED TO HAVE ITS AXIS CROSSED WITH RESPECT TO THE AXIS OF A COOPERATING ROLL TO PROVIDE AN EFFECTIVE CROWN ON SAID ONE ROLL; A CALENDER ROLL HAVING A CONTOUR ALONG ITS FACE PREDETERMINED BY THE DIFFERENCE BETWEEN A CROWN CONTOUR BASED UPON THE SHAPE OF A UNIFORMLY LOADED BEAM BETWEEN TWO POINTS OF SUPPORT, AND AN EFFECTIVE CROWN DEFINED BY THE DISTANCE BETWEEN ADJACENT SURFACES 